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Abstract:

Achieving site-selectivity in arene functionalization that is complementary to the one from electrophilic aromatic substitution (EAS) reactions has been a long-standing quest in organic synthesis. The palladium/norbornene (Pd/NBE) cooperative catalysis potentially offers a unique approach to this problem, but its usage has been hampered by 鈥渢hree constraints鈥�: the electrophile constraint, the arene-substrate constraint, which is the requirement of using aryl iodides, and the 鈥渙rtho constraint鈥�, which is the requirement of an ortho substituent for mono ortho functionalization of haloarenes. Here, we show that all these three constraints could be addressed through designing the electrophiles, phosphine ligands and norbornene ligands. Besides Catellani-type ortho alkylation and arylation, new ortho functionalization methods, such as ortho amination, acylation, carboxylation, thiolation and annulation, have been realized. In addition, using a unique phosphine system, various aryl bromides can be employed as the arene substrates. Moreover, a new class of bridgehead-modified NBEs overcomes the 鈥渙rtho鈥� constraint, thereby enabling a broadly useful strategy for arene functionalization with complementary site-selectivity to EAS reactions. A range of ortho-unsubstituted aryl iodides, previously problematic substrates, now can be employed to provide mono ortho functionalized products effectively. These methods are applicable for late-stage functionalization of complex bioactive molecules at positions that are difficult to be reached by conventional approaches. Beyond arene substrates, we also realized a non-intuitive transformation, that is to migrate ketone carbonyl to its adjacent position in one-pot through 伪-amination of alkenyl triflate. Conventionally, carbonyl 1,2-migration is a very tedious and less selective process, and generally takes 4-6 steps. This method not only provides a straightforward approach to access oxygen-transposed analogues, but also opens the door for a completely new type of carbonyl transformations.

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Bio:

Guangbin Dong received his B.S. degree from Peking University and completed his Ph.D. degree in chemistry from Stanford University with Professor Barry M. Trost, where he was a Larry Yung Stanford Graduate fellow. In 2009, he began to research with Professor Robert H. Grubbs at California Institute of Technology, as a Camille and Henry Dreyfus Environmental Chemistry Fellow. In 2011, he joined the department of chemistry and biochemistry at the University of Texas at Austin as an assistant professor and a CPRIT Scholar. Since 2016, he has been a Professor of Chemistry at the University of Chicago. Now, he is the first chair of the Weldon G. Brown Professorship.

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